RESUMEN
Aqueous zinc-ion batteries are regarded as promising and efficient energy storage systems owing to remarkable safety and satisfactory capacity. Nevertheless, the instability of zinc metal anodes, characterized by issues such as dendrite growth and parasitic side reactions, poses a significant barrier to widespread applications. Herein, we address this challenge by designing a localized conjugated structure comprising a cyclic polyacrylonitrile polymer (CPANZ), induced by a Zn2+-based Lewis acid (zinc trifluoromethylsulfonate) at a temperature of 120 °C. The CPANZ layer on the Zn anode, enriched with appropriate pyridine nitrogen-rich groups (conjugated cyclic -C=N-), exhibits a notable affinity for Zn2+ with ample deposition sites. This zincophilic skeleton not only serves as a protective layer to guide the deposition of Zn2+ but also functions as proton channel blocker, regulating the proton flux to mitigate the hydrogen evolution. Additionally, the strong adhesion strength of the CPANZ layer guarantees its sustained protection to the Zn metal during long-term cycling. As a result, the modified zinc electrode demonstrates long cycle life and high durability in both half-cell and pouch cells. These findings present a feasible approach to designing high performance aqueous anodes by introducing a localized conjugated layer.
RESUMEN
Designing efficient catalysts to promote the electrochemical oxidation of anodes is the core of the development of electrochemical synthesis technologies, such as HER and CO2 RR. Here, a novel vacuum induction strategy is used to synthesize nickel boride/nickel (Ni3 B/Ni) heterostructure catalyst for electrochemical oxidation of methanol into formic acid. The catalyst has extremely high reactivity (only 146.9 mV overpotential at 10 mA cm-2 , the maximum current density reaches 555.70 mA mg-1 and 443.87 mA cm-2 ), ultra-high selectivity (Faraday efficiency of methanol conversion to formic acid is close to 100%), and ultra-long life (over 50 h at 100 mA cm-2 ). In-suit electrochemical impedance spectroscopy proved that MeOH is oxidized first and inhibits the phase transition of the electrocatalyst to the high-valent electrooxidation products, which not only enables the high selectivity of MeOH oxidation but also ensures high stability of the catalyst. The mechanism studies by density functional theory calculations show that the potential determining step, the formation of *CH2 O, occurs most favorably in the Ni3 B/Ni heterostructure. These results provide references for the development of MeOH oxidation catalysts with high activity, high stability, high selectivity, and low cost.
RESUMEN
Due to the great advantages of low cost, high capacity, and excellent safety, the Zn metal is a promising candidate material for rechargeable aqueous battery systems. However, its practical applications have been restricted by the uncontrollable dendrite growth and electrode side reactions (such as corrosion, passivation, and hydrogen evolution reactions) during the plating process. Herein, we reveal that the dendrite growth would expose the electrode to more highly active tips, exacerbating the passivation of the electrode and the decomposition of the electrolyte by in situ optical microscopies. We propose a low-cost, nontoxic, low-concentration (less than 1 g/L), and effective electrolyte additive, saccharin sodium, which can guide an even Zn deposition without obvious electrode side reactions in the charge/discharge process. The saccharin anion acts as a "traffic assistant" of Zn2+ and demonstrates its great potential for practical application. The assembled Zn symmetrical battery shows an excellent cycling performance at a high current density and capacity (an extremely long cycle life over 3800 h is obtained at 5 mA/cm2 and 8 mA h/cm2, and 20 mA/cm2 and 5 mA h/cm2 show a lifetime over 800 h), and the full cell (coupled to an AC electrode) presents a stable cycle life with a capacity retention of 86.4% even after 8000 cycles at 5 mA/cm2. The saccharin sodium proposed in this work is promising to solve the anode problems in advanced Zn batteries.